During the operation of a washing machine, particularly during spin cycles, the machine can sometimes experience an extreme vibration. These vibrations can even cause displacement of the washing machine as it “walks” across a surface such as a floor. Typically, this event is due to the different shapes and densities of the clothing or other articles that are being washed which, after the washing cycle and draining the wash basket, can stick together and cause differences in the center of mass inside the wash basket. The vibration problem can also be caused by the introduction of relatively heavier articles into the wash basket such as e.g., shoes.
By way of example, after the washing cycle and draining of the washing liquid from the wash basket, the shoes or other, relatively heavier articles may be located on one side of the wash basket or in a manner that causes the center of mass of the combined wash basket and articles (such as the shoes, clothes, and other items being washed) to be off center. As the wash basket is rotated, particularly at high speeds, the off centering and centrifugal forces creates an imbalance that can generate undesired strain in the washing machine components, an undesirable level of noise, and/or “walking” of the appliance. In an extreme or prolonged situation, the imbalance created by the excessive vibration can also wear-out and damage the washing machine components.
As a result, in order to counter the out of balance wash load, various devices have been proposed. For example, washing machines have been equipped with balance rings, which are typically hollow rings placed on the top and sometimes bottom of the wash basket. Inside the ring (or toroid) a weight such as a fluid and/or movable metal objects such as e.g., solid balls have been inserted. During operation, the ring will act as a counterweight to the out of balance load of clothes because the fluid and/or solid balls will move to a position within the ring that counters the centrifugal forces created by the articles in the wash basket so as to balance the overall mass of the articles in the wash basket.
Thus, for balance rings that incorporate a fluid, during spinning of the wash basket the fluid must be able to redistribute so to act as a counterweight to an out of balance of mass of the articles in the wash basket. Sometimes, however, as the rotational speed of the wash basket increases during a spin cycle, one or more critical speeds (i.e. resonant modes) are reached. At these critical speeds, the translational motion of the balance ring can be severe enough distribute the fluid in a manner that prevents it from properly counteracting the out of balance wash load. In fact, the fluid may even be distributed in a manner that reinforces the tub motion.